Directional relay



p 1936. M. A. BOSTWICK 2,053,416

DIRECTIONAL RELAY Filed July 1, 1932 WITNESSES: INVENTOR My)" 0/1ABoszww/f.

AT RNEY Patented Sept. 8,1936

PATENT OFFICE DIRECTIONAL RELAY Myron A. Bostwick, North Arlington, N.1., assignor to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsylvania Application July 1, 1932,Serial no. 620,522

Clalms. (C l.175-294) My invention relates to protective apparatus forelectriccircuits and particularly to network protective apparatusoperating upon the phasesequence principle, as disclosed in thecopending 5 application of R. E. Powers and H. R. Searing, Serial No.648,207, filed December 21, 1932, and assigned to the WestinghouseElectric and Manu- Iacturing Company. In the above-mentioned applicationof R. E.

.10 Powers andH. R. Searing there is disclosed a novel form of networksystem in which the opening operation of the network protectors iscontrolled by means of single-phase directional elements energized inaccordance with positive sequence 15 power quantities, operating inconjunction with instantaneous overcurrent elements responsive topositive and negative sequence currents. In the operation of the Powersand Searing system, the network protectors connected to any feeder may?go be opened at will by opening the feeder circuit breakerand'artificially circulating negative sequence currents in the feeder,as explained in the above-mentioned application. Under these conditions,the directional elements respond to the g5 rever'sedilow of positivesequence power, and the negative sequence overcurrent elements respondto the negative sequence current, to cause the.

network protectors to open. However, reversed power flow at varioussupply points of the net- 30 work occurs frequently because ofregenerative operation of motors, variations of load distribution on thenetwork if supplied from more than one source, etc., and if, during sucha reversed power condition, a sumciently unbalanced mo- 35 mentarycurrent flows, one or more of the protectors open. It is, therefore,desirable to provide some means of distinguishing between the momentarynegative sequence current flow which may occur accidentally duringreversed power 40 conditions, and the sustained negative sequencecurrent flow artificially established to cause the protectors to open.In the former case it is desirable to prevent the opening of theprotectors.

It is accordingly an object of my invention to 45 provide an improvementof the above-mentioned invention of R. E..Powers and Searing which shalloperate to reduce the number of unnecessary protector operations. 1Another object of my invention is to provide a 50 "novel arrangement ofphase-sequence protective apparatus of general utility.

Other objects of my invention will become evident from the followingdetailed description taken in conjunction with the accompanying 5'drawing, in which the single figure is a diagrammatic view of aprotective arrangement embodying my invention.

Referring to the drawing, a circuit breaker I is provided for connectingan alternating-current source (not shown) and a polyphase load circuit 52. The circuit breaker i is provided with a closing coil 20 connected tosuitable energizing means, shown as a battery 4, by a switch 22, andwitha trip coil 3 connected to the battery 4 in a circuit which includesthe contact members 5 and 6 of an 10 induction disc relay, indicateddiagrammatically at i. For simplicity, I have illustrated the contactmembers of the relay 1 as a movable contact member 5 and astationarycontact member 6, but

I it will be understood that other arrangements duction disc 9. Thecontact member 6 is secured upon an index cylinder ill adjustablymounted, by means not shown, co-axially with the arc of travel of thecontact member 5, so that the contact member 6 may be secured in anyof anum ber of positions along the arc. A biasing spring. 8a is provided forrotating the spindle 8 so that a moving part of the relay is resilientlyheld against a stop member (not shown) in a position such that thecontact members 5 and ii are separated.

The induction disc 9 is positioned in the usual 0 manner so that it maybe influenced by an operator comprising a driving-magnet ii and a dragmagnet 9a. The driving magnet ii is preferably of laminated constructionand is provided with the usual current poles i2 and potential pole i3.The parts of the driving magnet i i connecting the current poles i2 andthe potential pole i3 are of restricted cross section to limit the fluxwhich may be developed in the poles.

A pair of current windings i 5 are mounted upon the current poles i2 anda voltage winding i5 is mounted on the potential pole iii; A lag loop orshading coil i6 is mounted upon the potential pole i 3 of the drivingmagnet H, to modifythe tripping characteristic of the relay in a well,known of current transformers ltb is provided for ch- 'taining aresultant current depending in phase relationship and magnitude upon thecurrent in the remaining conductor of circuit 2 and one of theconductors associated with current transformers tile. 7

The secondary windings oi the current trans= formers ltd are connectedin opposition and the circuit so formed is connected to opposite iunc=tion points of a quadrilateral network designated generally by thereference numeral Similarly, the secondary windings of current.transformers Hill) are connected in opposition and to the re= rnainingjunction points of the networla The four branches of the quadrilateralnetwork 25 include a reactor 28, a resistor 26, the coil of anover-current relay lid and the current windings i l of relay l and thecoil oi an over-=current relay ill) in series, respectively.

The constants of the various elements included in the quadrilateralnetwork 25 are related as fol-: lows: The reactance and resistance ofthe coil of relay lla are equal respectively to the sum oi thereactances and the sum of the resistance of the coiloi relay ilb and thecurrent coils i l of the relay l. relay llu plus the impedance ofreactor 26 equal the vector sum of the impedance relay illh, plus theimpedance of relay i l plus the impedance of resistor 2d. The anglebetween these two irn= pedance vectors must be 60.

The relationship of currents in such a quadrilateral networh isdescribed in U. S. Patent 1,726,928 to H. P. Sleeper, et ai, issuedSeptern= her 3, 1929 upon an application Serial No. 685,06ll

filed January 8, i924 and assigned to the Westinghouse Electric itManufacturing Company.

Asexplained in the aloove-mentioned patent, the currents in the branchesof the quadrilateral corresponding to branches in which the coils oi Irelays We and ill; are included, are directly proportional tosymmetrical components of the polyphase currents supplied to thenetwork. For one phase-rotation of currents in the circuit 2, the coilof relay We is energized in accordance with a negative phase-sequencecomponent and the coil of relay ill; is energized in accordance with apositive phase-sequence component. For the op-= posits phase rotation ofcurrent in the circuit i2,

the coils of relay Ho and lib are energized respectively, in accordancewith positive and negative phase-sequence components.

The voltage winding iilof the relay ll is con nected, in a circuit whichincludes the contact members of the over-current relays llc and lib inparallel, to a voltage phase-sequence network The voltage phase-sequencenetwork 26 coinprises a resistor i l and a reactor iii. The reactor Thevarious instrument transformer windings "'zfre connected in suchrelative direction that when voltage of normal phase sequence is appliedto the circuit Z,.the voltage network it supplies a The vector sum ofthe impedance of aooacio positive phase-sequence voltage component, and

the current network 25 supplies a positive phase= sequence currentcomponent to the coil oif-relay tin and the current coils Mi of relay land a negative phase sequence current component to the coil of relayfile. The coils of relay l are connected in such relative direction thatthe torque of the relay tends to cause engagement of con= tact membersand t (tripping contacts) in respouse to reversed positive phasesequence power.

The operation of the above described apparatus may be set forth asfollows: The switch is closed to complete a circuit for the closing coil2h to thereby close the circuit breaker i. The oil? cult 2 now drawspolyphase current of magnitude, unbalance factor and phase relationshipdetermined by the character or its connected load,

it the load on circuit 2 increases, the positive current phase sequencecomponents increase, and upon the occurrence of a predetermined load,the over-current relay llh closes to complete a circuit for the voltagewinding iiioi relay ll. As long as the direction of power flow isproper, i. e.,

left to right in the figure, the torque of the relay l is incorrect tocause a tripping operation and the contact member 5 remains disengagedfrom the contact member If the unbalance factor of the load is increasedby loading one phase morethan another, a nega= tive phase-sequencecurrent component flows in the relay lla.- Upon the occurrence of apredetermined degree of unbalance, the relay lllc closes. However, itthe direction or? power now is still proper, no tripping operationoccurs.

it the power flow in circuit 2 now falls to zero, the relays We and lllhdrop out. If a power reversal now occurs in the circuit 2, so that thedirection of power how is from right to left, and either the negativephase-sequence current coin= ponent or the positive phase-sequencecurrent component increases to sufiicient valueto close one of therelays lie and lit", respectively, the relay l operates with definiteor' variable time do lay, as described in connection with Fig. l, tocomplete a circuit for the trip coil 3. The circuit breaker i now tripsopen.

A reversal of power in the circuit 2, as described above, may resultfrom are-generative operation of a dynanio=electric machine fed iroincircuit 2, a synchronizing operation, a fault or from otherdisturbances. Assuming that it is caused Toy a regenerative operation orasynchroniziug opera= tion, the value of reverse current is, in general,

lower than that which is caused by the hack-feed to a fault. The relayll'h may, if desired, he of suchdeslgn that it responds only to faultcurrents, or may, if desired, be sensitive enough to respond to acomparatively low reverse current equivalent to the exciting current ofa transformer. The relay We may beso chosen that a tripping operationresults from any desired degree of unbalance of the reverse current.

I do not intend that the present invention tails, arrangement of partsor circuit connec= tions herein set forth, as various modificationsthereof may be effected without departing from the spirit and scope ofmy invention. I desire therefore, that only such limitatons shall he im=posed as are indicated in the appended claims.

i claim as my invention:

-i. in a polyphase alternating-current network system of the type inwhich an unbalanced elec-' trical condition is produced on a feeder tocause the opening of network circuit breakers con shall be restricted tothe specific strucural detil accents nected thereto, a network circuitbreaker, control for said circuit breaker including a faultdetectingdevice responsive to predetermined abnormal condition dependent at leastpartially upon a voltage concution, said device saving a voltageconnection, means for segregating a negative chase sequence condition ofthe current traversing circuit breaker, and a relay resuonsive to thesegregated negative phase sequence current condition for controllingconnection.

2. protective ior goolvn'nase al ternating-ciurent circuit, a circuit toc "'rolfing said circuit, oower responsive relay o Jerable time delayfor controlling said circuit breaker, said relag having current win"- inmeans and voltage winding means, means for utinuously energizing saidcur ut Winding n accordance with a current con 'on of sec d circuit,means for connecting voltage Winding means for energization accordanceitie a voltage condition of said circuit when said is in a predeterminedunbalanced elec rical condition, and means for connecting said voltageWinding means for energizaiion in accordance with said voltage conditionwhen a cur rent condition of said circuit exceeds a credo terminedvalue, whereby said relay is operable with time delay in response to apower condition of said circuit when either a predetermined unbalanced.condition or a predetermined current condition of said circuit exists.

3. in protective apparatus for a poly-phase alternating-current circuit,a circuit breaker for controlling said circuit, a power responsive relayoperable with time delay for controlling said circult breaker, saidrelay having curr nt means and voltage winding means, for continuouslyenergizing said cmrent means in accordance with a current condition ofsaid circuit, means responsive to a positive symmetrical component oithe polypiiase current of said circuit for connecting said voltageWinding means for energization in accordance with a volt age conditionof said circuit when said goositive component exceeds a predeterminedvalue, and means responsive ,to a negative symmetrical conc== nonent ofthe polyphase current of said circuit for connecting said voltageWinding means for energlzation in accordance with said voltage conditionwhen said negative component exceeds predetermined value.

4. In protective apparatus for a poly phase alternating-current circuit,a circuit breaker for controlling said circuit, a power responsive relayoperable with ti e delay for controlling said ci7:=- cult breaker, saidrelay having a current winding and a voltage winding, meansiorcontinuously energizing said current winding in accordance with asymmetrical component of the polypliase current of said circuit, meansfor segregating symmetrical component of the polyphase voltage or" saidcircuit, means for connecting said voltage winding for energization inaccordance said symmetrical voltage component when a predeterminedunbalanced condition of said circuit exists, and means for connectingsaid voltage Winding for energization in accordance with saidsymmetrical voltage component when a current condition or" said circuitexceeds a predetermined value, whereby said relay is operable with timedelay in response to a power condition of said circuit when either apredetermined unbalanced condition or a predetermined current conditionof said circuit erists.

5. In protective apparatus for a polyphase al= ternating-currentcircuit, a circuit breaker for controlling said circuit, a powerresponsive relay operable with tune delay for controlling said circuitbreaker, said relay having a current winding and a voltage Winding,means for continuously energizing said current winding in accordancewith a positive symmetrical component of the current of said circuit,means for segregating a positive symmetrical component of the polyphasevoltage of said circuit, means responsive to a. positive symmetricalcomponent of the current of said circuit for connecting said voltagewinding for energization Tm accordance with said voltage component, andmeans responsive to a negative symmetrical component of the current ofsaid circuit for connecting said voltage winding for energization inaccordance with said voltage component.

MYRON A. BOSTWIC'K.

